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linux/arch/x86/lib
Daniel Micay 6974f0c455 include/linux/string.h: add the option of fortified string.h functions
This adds support for compiling with a rough equivalent to the glibc
_FORTIFY_SOURCE=1 feature, providing compile-time and runtime buffer
overflow checks for string.h functions when the compiler determines the
size of the source or destination buffer at compile-time.  Unlike glibc,
it covers buffer reads in addition to writes.

GNU C __builtin_*_chk intrinsics are avoided because they would force a
much more complex implementation.  They aren't designed to detect read
overflows and offer no real benefit when using an implementation based
on inline checks.  Inline checks don't add up to much code size and
allow full use of the regular string intrinsics while avoiding the need
for a bunch of _chk functions and per-arch assembly to avoid wrapper
overhead.

This detects various overflows at compile-time in various drivers and
some non-x86 core kernel code.  There will likely be issues caught in
regular use at runtime too.

Future improvements left out of initial implementation for simplicity,
as it's all quite optional and can be done incrementally:

* Some of the fortified string functions (strncpy, strcat), don't yet
  place a limit on reads from the source based on __builtin_object_size of
  the source buffer.

* Extending coverage to more string functions like strlcat.

* It should be possible to optionally use __builtin_object_size(x, 1) for
  some functions (C strings) to detect intra-object overflows (like
  glibc's _FORTIFY_SOURCE=2), but for now this takes the conservative
  approach to avoid likely compatibility issues.

* The compile-time checks should be made available via a separate config
  option which can be enabled by default (or always enabled) once enough
  time has passed to get the issues it catches fixed.

Kees said:
 "This is great to have. While it was out-of-tree code, it would have
  blocked at least CVE-2016-3858 from being exploitable (improper size
  argument to strlcpy()). I've sent a number of fixes for
  out-of-bounds-reads that this detected upstream already"

[arnd@arndb.de: x86: fix fortified memcpy]
  Link: http://lkml.kernel.org/r/20170627150047.660360-1-arnd@arndb.de
[keescook@chromium.org: avoid panic() in favor of BUG()]
  Link: http://lkml.kernel.org/r/20170626235122.GA25261@beast
[keescook@chromium.org: move from -mm, add ARCH_HAS_FORTIFY_SOURCE, tweak Kconfig help]
Link: http://lkml.kernel.org/r/20170526095404.20439-1-danielmicay@gmail.com
Link: http://lkml.kernel.org/r/1497903987-21002-8-git-send-email-keescook@chromium.org
Signed-off-by: Daniel Micay <danielmicay@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-12 16:26:03 -07:00
..
.gitignore
atomic64_32.c
atomic64_386_32.S
atomic64_cx8_32.S
cache-smp.c
checksum_32.S x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
clear_page_64.S x86/asm: Optimize clear_page() 2017-03-07 08:28:00 +01:00
cmdline.c
cmpxchg8b_emu.S x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
cmpxchg16b_emu.S
copy_page_64.S x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
copy_user_64.S x86/uaccess: Optimize copy_user_enhanced_fast_string() for short strings 2017-06-30 09:52:51 +02:00
cpu.c
csum-copy_64.S x86/asm: Don't use RBP as a temporary register in csum_partial_copy_generic() 2017-05-05 07:59:24 +02:00
csum-partial_64.c x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
csum-wrappers_64.c
delay.c Prevent timer value 0 for MWAITX 2017-04-30 13:35:11 +02:00
getuser.S x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
hweight.S Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2016-10-14 14:26:58 -07:00
inat.c
insn.c
iomap_copy_64.S
kaslr.c x86/mm/kaslr: Use the _ASM_MUL macro for multiplication to work around Clang incompatibility 2017-05-05 08:31:05 +02:00
Makefile
memcpy_32.c include/linux/string.h: add the option of fortified string.h functions 2017-07-12 16:26:03 -07:00
memcpy_64.S x86/mce: Fix copy/paste error in exception table entries 2017-03-22 08:43:25 +01:00
memmove_64.S x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
memset_64.S x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
misc.c
mmx_32.c
msr-reg-export.c
msr-reg.S objtool, x86: Add several functions and files to the objtool whitelist 2017-06-30 10:19:19 +02:00
msr-smp.c
msr.c x86/msr: Cleanup/streamline MSR helpers 2016-11-16 10:23:02 +01:00
putuser.S x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
rwsem.S
string_32.c
strstr_32.c x86: move exports to actual definitions 2016-08-07 23:47:15 -04:00
usercopy_32.c x86: switch to RAW_COPY_USER 2017-03-29 12:06:28 -04:00
usercopy_64.c x86, dax, libnvdimm: remove wb_cache_pmem() indirection 2017-06-15 14:35:24 -07:00
usercopy.c x86: switch to RAW_COPY_USER 2017-03-29 12:06:28 -04:00
x86-opcode-map.txt x86/insn: perf tools: Add new ptwrite instruction 2017-06-27 11:58:04 -03:00